An aerial shot of the River Seine in Paris. The Eiffel Tower can be seen to the left.

Paris 2024 Olympics: is open-water swimming in the Seine safe?

Open-water swimming events at the 2024 Olympic and Paralympic Games in Paris could be scuppered by the Seine river, where bathing has been prohibited since 1923.

Faecal contamination of the Seine, which winds 777 kilometres through northern France, exceeded the bathing quality standard for safe swimming just two days before the men’s and women’s triathlon races. Athletes testing the waters before making the plunge to compete have become accustomed to such setbacks. Just a year earlier, the open-water swimming world cup and the para triathlon test event and mixed relay competition in the Seine were cancelled due to the low quality of the water. No wonder athletes were worried ahead of Paris 2024.

The Seine is burdened with an enormous population (12.3 million people live in the region surrounding Paris) and a low river flow that cannot easily dilute pollution. A 19th-century combined sewer system is expected to manage a lot of wastewater: rainwater flows over roads, fields and rooftops and enters the sewer system, accumulating oil, heavy metals, animal faeces and pesticides along the way.

Combined with untreated sewage from homes and businesses, sewer water flow often strains the capacity of the network and treatment plants. To prevent backflow, untreated wastewater is discharged into the Seine through 200 outlets. This is commonly known as a combined sewer overflow.

The result is a murkier river with less oxygen dissolved in it and a higher concentration of faecal bacteria. During one intense rainstorm, the level of E coli and Enteroccus bacteria discharged into the Seine from one outfall rose nearly 100 times compared to a dry weather period.

Climate change could degrade the river further. Regional-scale climate models project more short and sharp downpours during the summer. The years 2016, 2022, 2023 and now 2024 have all seen heavy rainfall during June and July.

Continues…

For the full article by Jamie Wilks and Lois Mougin visit The Conversation.

ENDS

Notes for editors

Press release reference number: 24/112

About Loughborough University

Loughborough is one of the country’s leading universities, with an international reputation for research that matters, excellence in teaching, strong links with industry, and unrivalled achievement in sport and its underpinning academic disciplines.

It has been awarded five stars in the independent QS Stars university rating scheme, named the best university in the world for sports-related subjects in the 2024 QS World University Rankings – the eighth year running – and University of the Year for Sport by The Times and Sunday Times University Guide 2022.

Loughborough is ranked 6th in The UK Complete University Guide 2025, 10th in the Guardian University League Table 2024 and 10th in the Times and Sunday Times Good University Guide 2024.

Loughborough is consistently ranked in the top twenty of UK universities in the Times Higher Education’s ‘table of tables’, and in the Research Excellence Framework (REF) 2021 over 90% of its research was rated as ‘world-leading’ or ‘internationally-excellent’. In recognition of its contribution to the sector, Loughborough has been awarded seven Queen's Anniversary Prizes.

The Loughborough University London campus is based on the Queen Elizabeth Olympic Park and offers postgraduate and executive-level education, as well as research and enterprise opportunities. It is home to influential thought leaders, pioneering researchers and creative innovators who provide students with the highest quality of teaching and the very latest in modern thinking.

Categories